Why the Hawkins class was not a natural rearmament candidate

Why did the Royal Navy not replace the Hawkins class's 7.5-inch battery with 4.5-inch guns?

The navy wanted to retire the ships, disliked the 7.5-inch system, and retained the class mainly because no immediate replacement could cover its role.

The Royal Navy did not regard the Hawkins class as a promising long-term platform. Its 7.5-inch gun was not a successful weapon in British service, and the ships survived largely because the fleet lacked enough replacements for their duties. Their dimensions and armament also became historical reference points for later treaty cruiser limits, giving them an awkward institutional legacy. A major rearmament would therefore invest scarce effort in ships the navy already hoped to discard.